Recovery and purification of antibiotics



' lation.

reaming. 25, 1950 RECOVERY AND PURIFICATION OF ANTIBIo'rIos Harvey E.-Album and Eric'G. Snyder, Philadelphia, Pa., minors to. Wyeth Incorporated,

Philadelphla, Pa., No Drawing.

:12 Claims.

This invention relates to the recovery and purification of antibiotics. More specifically, it relates to a two-step method of purification of streptomycin or streptothricin involving activated-carbon treatment of a solution of the antibiotic in combination with a subsequentselective preclpitation; the peculiar features of this method adapt'it particularly to. the treatment of eluates of broth adsorbates obtained in the production of stre tomycin or streptothricin, and the resulting I b combination of steps constitutes a new and ad- I vantageousantibiotic recovery method.

Streptomycin and 'streptothricin I are complex Q organic nitrogen bases possessing valuable antibiotic properties; They are,'respectively, prodl-lcts ofthe like processes of the microorganisms Streptomuces griseus and Actinomyces lavendulae,

Y and are found dissolvedin culture broths on or i in which; the'organisms are grown. These antibiotics may be recoveredjby treating clarified broth with anactivatedcarbon adsorbent such as an appropriate grade of Nuchar (Virginia Pulp and Paper Co), Norit (American Norit Co.) Darco (Darco Corp), or the like, and elutingthe carbon with dilute methanolic hydrogen chloride after washing the carbon successively wlthwater,

acetone and methanol. The elution may advantageously be carried out in twosteps. The eluates, separately or combined, may then be adjusted to a pH of 6-6.5,settled, clarifledand concentrated at a low temperature by vacuum distil- The crude hydrochloride of the antibiotic may Streptomycin-and streptothricin are quite similar in manyvof theirphysical and chemical properties, such fas'in their solubility in water, lower alcohols and lower ketones'in their adsorbabllity,

a corporation of Delaware Application January 9, 1846,, Serial No. 640,140

' generally having Preparations of the former of high potency and plication to its recovery and purification. The application of the invention to streptothricin, however, will also be illustrated.

In the case of streptomycin the separated and dried precipitate obtained as described above is a crude streptomycin hydrochloride preparation a potency'of approximately to .70 units permilligram'(u./mg.) but occasionvally running as high as 100 u./mg. or more. The potency appearsto depend to a considerable ex- I tent on the potency of the broth and varies in the samesense. Typical broths have potencies of approximately 40 to 100 u./ml. The potency, also varies, roughly, inversely as the yield, higher potencies being obtainable under modified conditions with a sacrifice of yield.

The potency of streptomycin preparations, both solid and in solution, is determined by an agar-cup method similar to that used in assaying penicillin,

the testmicroorganism used for streptomycin being B. subtilis.

Comparison is made with a standard preparation referred ultimately to a crystalline streptomycin base as unity, i. e. 1000 u./mg., llghe "unit being one microgram of crystalline ase. Present tentative minimum specifications call for a streptomycin product having a potency of at least 200 u./mg., substantially free of pyrogenic and histamine efiect, and non-toxic.

Various methods have been proposed for purifying crude streptomycin and steptothricin.

. purity have been reported. For example, Fried be precipitated from the-concentrated residue by the addition of 2-3 volumes oi ether or. 10-15 volumes }ofacetone.; Usuallytheprecipitate is redissolved iii-methanol ,and reprecipitated'.

and in theirreactions asorganic bases with acids. v

.Accordingly, the present invention may be applied to the recovery and purifications of either one. Biologically, however, streptomycin and streptothrycin differ and are readily distinguishable by obiective tests For example, their toxic- -ities to higher animals dilfer, their antibiotic actions on microorganisms-bacterial spectra"- are diilerent, and streptomycin is, but-streptothrlcin' isnot, inhibited bycysteine in antibiotic activity.- H I At present streptomycin appears to be clini- I cally the more important oi -the two antibiotics,

7 and our invention will be illustrated chiefly by apand Wintersteiner (Science, 101, 613-615, June 15, 1945) used the so-called reineckate for purification, a crystalline salt resulting from reaction of streptomycin with Reinecke salt, NH4[Cr(SCN)4(NH3)-2]. Kuehl et al. (Science, 102, 34-35, July 13, 1945) report the preparation of a crystalline helianthate by treating in aqueous methanol solution of highly purified streptomycin hydrochloride with methyl orange. The helianthate may be converted to a hydrochloride having a potency of 800 u./mg. Peck et al. (J. Am. Chem. Soc., 67, 1866-1867, October 1945) report the preparation of a crystalline streptomycin- CaClz double salt by treating the hydrochloride or helianthate with methanolic CaCl-z. Carter et al. (J. Biol; Chem., 160, 337-342, September 1945) report on a chromatographic method of obtaining streptomycin fractions of high potency-520400 u./mg. Similar chemical purification methods have been published for streptothricin.

. j These reported methods prove that it is possible to produce streptomycin and streptothricin preparations of high potency and purity. They solution. In the present invention these exail. however, appear to require a starting machange t l l are ed in the active form, terial of relatively high potency or to involve the in a I condition to fle t substantial use of unusual reagents or complicated equip-v tranzation of t t t l tion, when inacment or to require extensive and careful control 5 tivated by use they are reactivated. e. g. by treatin operation or to result in a low yield of product. mg with a sodium b nate solution. They an appeal be methods of a laboratiry Best results are obtained by carbon-treating type; mme appears to combine the Simplicity of relatively dilute solutions, a. g. those having nooperation, employment of cheap readily availteneies f approximately 50 to 300 ulml" prefable materials and ability to give high yields'of m erably approximately 100 to 200 u./ml. The inproduct desirable in a large-scale commercial ventien, however, is workame ith more concenopel'ationtrated solutions, e. g. 600-700 u./ml-, with the It is one object of our invention to provide a sacrifice f considerable d, since more dilute simple and economical method of increasing the solutions give tt results b th as to potency Potency of streptomycin streptothricin prep l5 and yield, the limiting factor is largely economic, nations viz. the cost and consumption of solvents and pre- It is another object of our invention to provide eipitants and the best conditions will be detera method of streptomycin or streptothricin purimined in considerable part by the size of operafication which requires only relatively cheap and ens emciency of l ent-recovery equipment readily available materials so and the like. Because dilute solutions are pre- It is a further object of our invention to proferred, our invention is particularly applicable vide a meflmd Prfilducing high Yield Strepto the treatment of eluates obtained in streptotomycin or streptothricin of greatly increased pomyem and streptothricin roduction. Examples tency from crude streptomycin or streptothricin are given below Of relatively low g While ethanol and ethanol-water mixtures Other objects and advantages of our invention have been em loyed in streptomycin recovery, will be apparent from the following description. we have found t l t he the preferred 801- According to our invention, we obtain streptovent for use in our process, The ethanol used mycin streptothricin of increased potency should have a low water content, preferably not spectively from crude streptomycin or strepto- 30 over about w t higher water content, e. g. thricin by a two-step treatment of a solution of 10%, there is a greater but less selective adsorpthe crude antibiotic, such as the eluate of the eion f solids by t ti ted carbon in our first adsorbate from the broth obtained in convenstep, and a greater tendency for the streptomy tional streptomycin or streptothricin production hydrochloride t he gummy in our second Step.

as described above- The two steps of our An excessive water content thus contributes both fication are (1) treatment of the solution with to lower yield and l r otency of the final activated carbon under specific conditions, and product (2) selective precipitation of streptomycin or Ethyl ether may b sed as the precipitant in streptothricin from the filtrate from step (1). our second tep d ha the advantage that on y we have discovered for example that if a 2-3 volumes are required. We preferto use acedilute, approximately neutral methanol solution tone however, in lt f the fact that 10-15 volof crude streptomycin hydrochloride is agitated mes t be d, Among the reasons for th s at room pe a i a small percentage of preference are: less sensitivity to the presence of a suitable activated carbon such as ,Nuchar water in t methanol, less tendency to form 0-1000, filtered and mixed with 10-15 volumes of my precipitates, greater selectivity in precipi. acetone, a high yield of streptomycin hydrochlotench especially as respects inorganic s l ride of substantially increased potency is obhigher b ili int and somewhat less fire haztainedard. Dioxane can also be used satisfactorily in The acidity of the methanol solution should be place f acetone in substantially the Same adjusted to pH 3-7, preferably pH 6-7, for best nts, results. Substantial purification can, however, Th following examples illustrate the degree of be obtained by treating with activated carbon purification effected and the yields obtained in Solutions of S p y in methanol at P practicing our invention. These examples are 8- filtering and precipitating intended to be illustrative only, and not to limit Acid methanol solutions of streptomycin may our invention, the scope of which is defined in be brought to a suitable pH value by the addition the appended claims. of methanolic NaOH or KOH. Since, however,

this results in the formation of inorganic sodium Examp 1 or potassium salts which must later be removed, A Solution f crude t t myci hydrochloride we prefer to efiect this adjustment by contact of so in substantially ater free methanol was the solution with a- Solid anion-exchange pared; the reaction was nearly neutral (pH 6-7).

terial such, for example, as Amberlite IR-4 (sold The crude streptomycin had a, potency of 40 by the Resinous Products and Chemical Co. of and the Solution had a potency concentra- Philadelphia) or equivalent. These materials tion f 133 1 sev nty-five ml. portions o are sold and ordinarily used with a substantial as the solution were t t d respectively, with the water content; they are inactive when completely amounts of ti t d carbon indicated in the dry. They would not be satisfactory for our purtable by tirring lution and carbon at roo poses in the wet form, since they would introduce temperature for approximately a. half hour and an undesired amount of water into the methanol fi1te1-ing Sixtv m1. ortions of the nitra e w solution. It has been found, however, that if 7 stirred ith 900 ml. portions of acetone; the Prethey are sucked dry on a vacuum filter, slurried cipitates ere collected, dried an fl with methanol and drained, they may be brought The results are summarized in the followin to a state of reduced water content in which they table in which: the first column gives the will still effect anion exchange without introducamount of carbon used in grams per hundred ing any deleterious amount of water into the 7 illiliters of solution, i. e. weight-volume percent:

the second column gives the total units of potency found by assay in each portion of solution after carbon treatment: 'thethird, column gives D centage of potency remaining after carbon treatment-taking the potency oflthe sample treated with 0.0 carbon (first line of table) as 100: and the fourth column gives the potency per milligram of the several precipitates.

Under the conditions of these experiments the optimum amount of carbon was 2-3%; loss by treatment with 2% carbon was only 6%; ratio of increase of potency with precipitation only was approximately 2, with ,2%carbon plus precipitation. 8, and with 3% carbon plus precipitation, over 9.

. Example 2 I That neither carbon treatment alone nor precipitation alone will eifect the purification achievedby our invention is further shown by the following experiments.

a. A 75 ml. portion of a. streptomycin HClmethanol eluate was adjusted to a pH of 6.6; the eluate had a potency of 102 u./ml., the dissolved streptomycin hydrochloride, 34 u./mg. The eluate was stirred for 20 minutes with 2% Nuchar C-1000 and filtered. A portion of the filtrate was evaporated to dryness in a vacuum desiccator; the residue assayed 31 u./mg. Another portion of the filtrate was stirred with volumes of acetone; the dried precipitateassayed 216 u./mg. In this experiment carbon treatment alone failed to increase the potency of r the product,

. while carbon treatment, followed by selective precipitation, increased the potency approximately sixfold.

b. A methanolsolution of streptomycin hydrochloride was prepared'having a potency of 138 u./ml.; the dissolved material had a potency of 40 u./mg. A portion of this solution was mixed with 15 volumes of acetone; the dried precipitate assayed 67 u./mg. Another portion of the solution was treated with 3% activated'carbon as i experiment a. and filtered. The filtrate was mixed with 15 volumes actetone; the dried precipitate assayed 340 u./mg.

In this experiment acetone precipitation alone caused onlya moderate gain in potency (approximately 70%), while carbon treatment followed by precipitation eifected more than an eightfold. increase in potency.

Example 3,

The following experiment illustrates the application of our'invention to streptothricin.

A solution-of streptothricin hydrochloride in methanol was made up and adjusted to a pHof 6.9; the potency of the solution was 380 u./ml'.

r. and of the'dissolVed streptothricin hydrochloride 67 u./mg., -The solution was divided into two portions,:one of which was treated with 4 percent activated carbon (Nuchar C4000) pH 6.9 and the other of which'was treated with 4 percent of the same'carbon after having been made 0.1 N

acid by adding small amount of concentratedaqueous am. After stirring with the carbon atroom temperature for approximately hour, the two portions were filtered and the total potencies of each filtrate determined by assay. The nearly neutral solution (pH 6.9) retained 75 percent of its total potency and the slightly acid solution (0.1 N. H01) retained 82 percent. The portions were each separately. mixed with a, large excess of acetone, the precipitates separated and dried, and their potencies determined. The precipitate from the nearly neutral solution had a potency of 170 u./mg., while that from the slightly acidsolution had a potency of 141 u./mg. The two-step treatment thus resulted in each case in a more than twofold increase in potency.

Example 4 The application of our method to streptomycin in a weakly alkaline alcoholic solution is illustrated in the following experiment.

A methanol solution of streptomycin hydrochloride having a potency of 40 u./mg. was prepared, the solution having a potency of 500 u-./ml.

The pH of the solution was raised to 8.5, the solution stirred for hour with 2.5 percent activated carbon (Nuchar (3-1000) and filtered. The basic streptomycin compound was precipitated with acetone, dried, weighed and assayed. Its

. potency was 114 u./mg. and the overall yield,

' eluates were then equivalent to:

based on potencies. was 44 percent.

The basic compound was dissolved in methanol, 1.92 g. in 400 ml. methanol. The solution was stirred with 1 percent activated carbon (Nuchar C-1000) and filtered. The filtrate was then acidified by the addition of concentrated HCl. The hydrochloride was precipitated with acetone, dried, weighed and assayed. Its potency was 347 u./mg. and the yield of this stage, based on potencies, was 55 percent. The combined yield of the twostages, each comprising a carbon treatment and selective precipitation, was 24 percent.

Example 5 The application of our two-step purification methodto streptomycin recovery from broth obtained in streptomycin production is illustrated in the following experiments.

a. Three hundred and fifty liters of a broth from a surface culture of .S'treptomyces griseus, having a potency concentration of 73.5 u./ml. (average of two liter portions) and an approximate antibiotic content equivalent to 25,- 725,000 u., was stirred for V hour, after clarification, with 1.5 percent activated carbon (Nustirring hour at room temperature and filtering. Therespective antibiotic activities of the Units Eluate 1 14,030,000 Eluate 11 3,770,000

Total 17,000,000

representing 69 percent of the original antibiotic activity of the broth.

g The carbon-treated eluates were then evaporated to small volume insvacuo, eluate I to 1.9 l. and eluate II to 1.4 1. Each concentrate was mixed with a large volume of acetone after clarification, and the resulting precipitate separated, dried and assayed.

Eluate I yielded 57.7 g. streptomycin hydrochloride having a potency of 210 u./mg. or a total potency of approximately 12,117,000 11. The

yield from eluate II was 27.7 g. having a po- 600,000 u., was stirred for L hour, after clarification, with 1 percent activated carbon (Nuchar XXX) and filtered. The carbon adsorbate was washed as in experiment a, all washings showing zero potency. The washed adsorbate was then eluted with two successive 28-1. portions of 0.1 N methanolic HCl. The first eluate (I) had antibiotic activity equivalent to 6,860,000 u., the sec-- and (II), 1,036,000 11. The total activity of the two eluates was 7,896,000 u., or 58 percent of the antibiotic activity of the broth.

,On precipitation with acetone as in experiment a, but without carbon treatment, eluate I yielded 65.6 g. streptomycin hydrochloride having a potency of 97 u./mg., or a total of 6,363,000 u.. and eluate II yielded 24.8 g. having a potency of 45 u./mg., Or a total of 1,115,000 11. The combined potencies of the two fractions was 7,478,- 000 u.; this represents a yield, in terms of potencies, of 55 percent of the total broth potency and 95 percent of the potencies of the eluates.

From the data of this example (12) it will be seen that the application of our invention to the recovery of streptomycin from broth resulted in a product of greatly improved potency, while the percentage yield, based on potencies, was maintained at an economically practical level.

In all the above examples the stated percentages of activated carbon used to treat the various so lutions mentioned are in terms of weight volume percent; e. g. a treatment with 1 percent activated carbon involves using g. activated carbon per liter of solution.

Our invention may be applied not only to the hydrochloride but also to other water-soluble salts of streptomycin such as the sulfate.

We claim:

1. The process of purifying an antibiotic selected from the group consisting of the water-soluble salts of streptomycin and streptothricin which comprises: treating a dilute faintly-acid-to-neutral solution of said antibiotic in a saturated alcohol containing not more than two carbon atoms with a small percentage of activated carbon adapted to condition the carbon-treated solution to yield an antibiotic of enhanced potency by selective precipitation, removing the carbon, and selectively precipitating an antibiotic of enhanced potency from the carbon-treated solution by adding thereto a volatile oxygen-containing organic liquid which is a non-solvent for the antibiotic and is miscible with the solution.

2. The process defined in claim 1. in which 8 selective precipitation is eflected by adding to the carbon-treated solution a mono ketone containing not more than four carbon atoms in the molecule.

3. The process defined in claim 1, in which selective precipitation is eflected by adding to the carbon-treated solution an ether having no more than four carbon atoms in the molecule.

4. The process defined in claim 1, in which selective precipitation is effected by adding acetone to the carbon-treated solution.

5. The process defined in claim 1, in which the carbon-treated solution has a pH in the range 37 and contains less than 10 percent water.

6. The process of purifying streptomycin, which comprises: preparing a dilute methanol solution of a water-soluble salt of streptomycin, said methanol solution having a pH in the range 3-7, agitating the solution with a small percentage of activated carbon adapted to condition the carbontreated solution to yield streptomycin of enhanced potency by selective precipitation, removing the carbon, and selectively precipitating streptomycin of enhanced potency from the carbontreated solution by mixing with the solution several times its volume of a non-solvent for streptomycin selected from the group consisting of ethyl ether, acetone and dioxane.

7. The process of purifying streptomycin hydrochloride, which comprises: agitating a dilute methanol solution of streptomycin hydrochloride having a pH in the range 3-7 with a small percentage of activated carbon adapted to condition the carbon-treated solution to yield streptomycin of enhanced potency by selective precipitation, removing the carbon, and selectively precipitating streptomycin hydrochloride of enhanced potency from the carbon-treated solution by mixing with the solution a multiple volume of acetone.

8. The process defined in claim 6, in which the methanol solution prior to carbon treatment has a potency concentration of not over 300 u./ml. and after carbon treatment has a pH in the range of 6-7 and a water content of not over about 3 percent.

9. The process defined in claim 6, in which a. carbon-treated methanol solution of streptomycin hydrochloride having a pH in the range 6-7 and a water content of not over about 3 percent is subjected to low-temperature concentration prior to selective precipitation.

10. In a process of recovering an antibiotic from a culture broth containing said antibiotic, said antibiotic being selected from the group consisting of streptomycin and streptothricin, which comprises adsorbing said antibiotic to a solid adsorbent, removing from the resulting adsorbate unadsorbed broth constituents and water, and eluting the adsorbate with a dilute methanol solution of an acid which forms a watersoluble salt with said antibiotic and is of suflicient strength to remove said antibiotic from the adsorbate, the improvement which comprises: regulating the elution to yield an eluate having a potency concentration of not over about 600 u./ml., adjusting the pH of the eluate to fall within the range 3-7, agitating the eluate with a small percentage of activated carbon adapted to condition the carbon-treated eluate to yield an antibiotic of enhanced potency by selective precipitation, removing the carbon, and selectively precipitating the antibiotic from the carbon-treated eluate by mixing with the eluate several times its volume of a non-solvent for the antibiotic selected from the group consisting of ethyl ether, acetone and dioxane.

11. In the recovery 01 an antibiotic of the group consisting of streptomycin and streptothricin from a culture broth containing said antibiotic by a process in which said antibiotic is adsorbed to a solid adsorbent and then eluted therefrom with a dilute methanol solution of an acid forming a water-soluble salt with the antibiotic, the steps which comprise treating the resulting eluate ata pH of 3-7 with activated carbon adapted to condition the carbon-treated eluate to yield an antibiotic of enhanced potency by selective precipitation, removing the carbon, and selectively precipitating an antibiotic or enhanced potency by mixing with the carbon-treated eiuate several times its volume of a non-solvent for the antibiotic selected irom the group consisting oi ethyl ether, acetone and dioxane.

io 12. The steps defined in claim 10, in which the eluate contains streptomycin hydrochloride, its potency concentration is not over about 300 u./mg., and its water content not over about 3 percent.

HARVEY E. ALBURN.

ERIC G. SNYDER.

REFERENCES CITED The following references are of record in the file of this patent:

Cheronis: "Semimicroand Macro-Organic Chemistry" (New York, Crowell, 1942), pages 207-210.

Schatz et al.: Proc. Soc. Exptl. Biol. Med., vol. 55 (1944) pages 66-69.

Waksman (2): J. Bact., vol. 46 (1943). pages 299-310. 

1. THE PROCESS OF PURIFYING AN ANTIBIOTIC SELECTED FROM THE GROUP CONSISTING OF THE WATER-SOLUBLE SALTS OF STREPTOMYCIN AND STREPTOTHRICIN WHICH COMPRISES: TREATING A DILUTE FAINTLY-ACID-TO-NEUTRAL SOLUTION OF SAID ANITIBIOTIC IN A SATURATED ALCOHOL CONTAINING NOT MORE THAN TWO CARBON ATOMS WITH A SMALL PERCENTAGE OF ACTIVATED CARBON ADAPTED TO CONDITION THE CARBON-TREATED SOLUTION TO YIELD AN ANTIBIOTIC OF ENHANCED POTENCY BY SELECTIVE PRECIPITATION, REMOVING THE CARBON, AND SELECTIVELY PRECIPITATING AN ANITBIOTIC OF ENHANCED POTENCY FROM THE CARBON-TREATED SOLUTION BY ADDING THERETO A VOLATILE OXYGEN-CONTAINING ORGANIC LIQUID WHICH IS A NON-SOLVENT FOR THE ANTIBIOTIC AND IS MISCIBLE WITH THE SOLUTION. 